Set the front end of the saw s flat blade plate on the damaged board with the blade held up off the surface and pointing in the same direction as the length of the floorboard.
How to fix a low spot in a wood floor.
If you need to bring down your subfloor you can try either a hand plane or a power sander.
High spots and bumps in subfloor.
This requires using a laser level to pinpoint the low areas and attaching the shims working on bare joists above a basement or crawlspace by gluing and screwing them to the joists.
Use an underlayment floor leveler or floor patch product to fix low spots in a wood or concrete subfloor.
An underlayment is a thin layer of material sandwiched between two other materials.
Water based urethane will dry clear while oil based formulations will impart a slight golden.
It can also serve as a vapor barrier.
If your floor is natural unstained wood then try a few types of floor urethane on your test patch.
Start the saw and lower the blade into the wood.